In particular, the present invention relates to an actuating assembly, for example of the type illustrated in FIG. 1A, for displacing a general operative member according with a roto-translation motion, and in the particular example described for displacing a funnel, or a baffle, or even a blowing head of an I.S. machine, respectively to convey a gob of glass into a glassware forming mold, to close an upper opening of the forming mold itself and to blow air into the inner cavity of the glassware being formed and make it assume the final shape.
The aforementioned roto-translation motion is obtained by combining a translation along a vertical axis to and from the forming mold and a rotation about the vertical axis itself from and to an operative position, in which the baffle, the funnel, or the blowing head are coupled to the forming mold.
Specifically, in FIG. 1A, reference G indicates a generic known actuating assembly, which extends through a box L of the machine and comprises a fixed frame T, a supporting shaft H of the operative member N coupled to the fixed frame coaxially to the vertical axis, a linear actuator B for translating the shaft along the vertical axis, a cam and tappet device C for rotating the shaft about the vertical axis itself and a hydraulic damping cartridge D for braking the operative member when it is arranged near its raised end-of-stroke position along the vertical axis. The damping along the stretch near the lowered end-of-stroke position, on the other hand, is performed by controlling the pneumatic actuator and varying, for example, the compressed air exhaust passage section.
The hydraulic damping cartridge is arranged over the linear actuator and the box and by the side of the shaft, and is connected to a dedicated hydraulic circuit H thereof.
On the other hand, the tappet and carts device is arranged under the linear actuator and comprises a fixed cam defined by a groove obtained in a side wall of a tubular body and a tappet element radially overhanging from a lower free end portion of the shaft and plunging into the tubular body. The cam has an upper ramp stretch and a lower stretch substantially rectilinear and vertical. The cam device is lubricated by means of oil accommodated in the tubular body.
Although universally used, the known actuating assemblies of the type described above are not very satisfactory for the following reasons.
First of all, despite being controlled by the hydraulic cartridge and by means of the pneumatic actuator, the known assemblies do not allow a smooth, controlled displacement of the operative member, which vibrates during its displacement oscillating forwards and backwards not only in the intermediate stretches comprised between the terminal end-of-stroke stretches but also in the ends-of-stroke stretches themselves.
The unexpected motion variation, for a part, is generated by the reciprocating motion of the pneumatic actuator and, for another part, is consequent to the geometry of the cam, the ramp section of which generates an obstacle to the movement during descent, which however fails immediately when the tappet element runs under the vertical stretch. In such a condition, the piston of the linear actuator undergoes a sudden acceleration which causes sudden variations of volume in both the upper chamber fed with compressed air and the lower chamber which is exhausting. The feeding of compressed air is not sufficient to avoid a lowering of the pressure in the feeding chamber, whereas the exhaust is not sufficient to avoid a raising of the pressure in the exhaust chamber. In many cases, the pressure variations in the mentioned chambers slow down or even stop the piston, which then suddenly restarts as soon as the pressures rebalance. Such faults cannot be overcome by acting on the pneumatic system.
As a consequence, the operative member often couples with the forming mold when the vibrations have not been exhausted or damped yet, so that relative sliding is generated, which generates early wear on both the mold and the operative member.
Besides, the shocks that the actuating member undergoes when the operative member reaches the molds or the actuator reaches the end of stroke, lead to early wear of the components of the actuating assembly itself.
Furthermore, because of the extremely small spaces in the cam zone, the radial loads transmitted by the tappet element to the plunging end portion of the shaft cannot be supported by inserting a supporting bearing or a bushing, and thus the end portion always works overhangingly with inevitable anomalous wear of the cam/tappet assembly.
Additionally, during the upward and downward movements of the shaft, the mentioned plunging end portion generates significant variations of volume in the mentioned tubular body, in which the lubricant oil is present, and it triggers pumping phenomena, which cause a progressive emptying of the tubular body because the oil either exits outwards or moves up the shaft and enters into the pneumatic cylinder.
Besides, the aforesaid known assemblies are not very safe because the presence of the damping cartridge by the side of the shaft, and thus in position close to the forming mold, implies the presence of flammable lubricant oil in a very hot tone of the machine itself, and consequently there is a real fire risk in case of leakage of oil from the cartridge or from the oil feeding circuit.
Furthermore, for the reasons above, the known assemblies do not allow to reduce the displacement times of the operative members beyond a given threshold and thus to increase the production rate of the forming machine in safe manner.